Study objective-To estimate the net financial benefit of neonatal screening for phenylketonuria (PKU) : by a simple pooling of cost data from the literature ; and by a more complex modelling approach.

Design-A systematic literature review was conducted to identify papers containing data on the monetary costs and benefits of neonatal screening for PKU.

The methodological quality of the studies was appraised, and data were extracted on resource use and expenditure.

Monetary data were converted to common currency units, and standardised to UK incidence rates.

Net benefits were calculated for median, best case and worst case scenarios, and the effect of excluding poor quality studies and data was tested.

The net benefit was also estimated from a model based on data from the literature and assumptions appropriate for the current UK situation.

Extensive sensitivity analysis was conducted.

Main results-The direct net benefit of screening based on the median costs and benefits from the 13 studies identified was £143 400 per case detected and treated (£39 000 and £241 800 for worst case and best case scenarios respectively).

The direct net benefit obtained by the modelling approach was lower at £93 400 per case detected and treated.